NCERT Class 11-Biology: Chapter – 15 Plant Growth and Development Part 8 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 15:

Both animals and plants grow. Why do we say that growth and differentiation in plants is open and not so in animals? Does this statement hold true for sponges also?


We say that growth and differentiation in plants is open and not so in animals despite both growing is because the plant growth and differentiation of certain parts like the meristematic tissues of the meristems present in different locations of the plant body is an active site of cell division where growth is indefinite. The cells keep on dividing at the meristems and hence growth occurs indefinitely. Because new cells are constantly added to the body of the plant it is called open growth.

Yes, this statement shall hold true for sponges as well.

Question 16:

Define parthenocarpy. Name the plant hormone used to induce parthenocarpy.


Parthenocarpy is the natural or artificial induced development of fruit without the fertilisation of ovules. This process of development of fruit was introduced in the year 1902. Examples of fruits showing parthenocarpy naturally are grape, orange etc.

The plant hormone used to induce parthenocarpy is Gibberellin. Auxin is responsible for inducing parthenocarpy in tomatoes.

Question 17:

While eating watermelons, all of us wish it was seedless. As a plant physiologist can you suggest any method by which this can be achieved?


A method by which watermelons can be produced seedless is parthenocarpy. Parthenocarpy is the natural or artificial induced development of fruits without the fertilization of ovules or formation of seeds.

Growth hormones can induce parthenocarpy like Gibberellins and auxins inducing parthenocarpy in tomatoes.

Question 18:

A gardener finds some broad-leaved dicot weeds growing in his lawns. What can be done to get rid of the weeds efficiently?


To get rid of the weeds efficiently, it can be selectively killed using plant growth hormone regulator called auxins.

Dicot weeds grow by apical shoot meristem growth whereas the grasses usually have the presence of intercalary meristems. When plant growth hormones like auxins is applied, it causes damaging effect on the shoot meristem thus destroying the dicot weeds and has no effect on the lateral meristem keeping grasses intact without a damaging effect. Hence the weeds are selectively destroyed.

Question 19:

On germination a seed first produces shoots with leaves, flowers appear later,

a. Why do you think this happens?

b. How is this advantageous to the plant?


a. When a seed germinates, it first produces shoots with leaves. This means that the plant enters the vegetative growth phase. During this phase florigen is synthesized which is a flowering hormone. It induces flowering in plant.

b. It is advantageous to plants as the vegetative phase prepares the plants for the reproductive phase so that it can bear structures like fruits and seeds.

Question 20:

Fill in the blanks:

a. Maximum growth is observed in ________ phase.

b. Apical dominance is due to ________

c. ________ initiate rooting

d. Pigment involved in Photo perception in flowering plants is ________


(a) Exponential

(b) Auxin

(c) Cytokinin

(d) Phytochrome

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